The present invention relates generally to the field of fluid flow control and, more particularly, to a system and method of pulsed detonation injection for fluid flow control of inlets, nozzles, and lift fans.
Various aircraft, such as tactical aircraft, have one or more jet engines that produce thrust corresponding to the exhaust coming from a nozzle of the jet engine. The weight and cost of tactical aircraft exhaust systems have increased at an alarming rate with the incorporation of features for afterburning, thrust vectoring, and advanced shaping. Historically, afterburning and vectoring have required variation of the nozzle geometry. For example, a typical turbo fan engine""s nozzle throat area must increase in size when afterburning. Vectoring has required deflection of nozzle flaps, and sometimes rotation of the entire nozzle assembly. Aperture shaping for afterbody integration further imposes the use of less structurally efficient two-dimensional, rather than axisymmetric, nozzles. These capabilities require greater mechanical complexity in the various systems.
One way to simplify the nozzle geometry and complexity, while reducing the weight and cost of jet engines and their associated nozzle configurations is to inject a crossflow into the primary flow. For example, U.S. Pat. No. 6,112,512 (the ""512 patent) issued to Miller et al., provides a method and apparatus for pulsed injection for improved nozzle flow control. The ""512 patent uses engine bleed from the compressor of the jet engine to inject air as a pulsed crossflow into the primary flow in the nozzle. However, bleeding air from the engine takes away mass flow rate of the primary flow, which reduces the thrust and efficiency of the jet engine. Therefore, ways to reduce and amplify compressor bleed air using pulsed detonation devices for controlling the nozzle jet is desired.
Another component associated with a tactical aircraft is a lift fan. Lift fans, which are typically driven by a shaft from a jet engine, produce thrust to aid in lifting of the aircraft. Because of the weight of tactical aircraft, lift fan systems can be very complex and expensive to obtain the required amount of thrust. Therefore, ways to simplify lift fan systems and still produce the required thrust are desired.
According to one embodiment of the invention, a system for altering a fluid flow includes a nozzle having a fluid flow and including a converging portion, a diverging portion downstream of the converging portion, and a throat coupling the converging portion to the diverging portion, at least one port located in a wall of the nozzle and angled with respect to the fluid flow, and at least one pulse detonation device operable to inject a plurality of detonation waves in a pulsed manner through the port and into the fluid flow. The pulsed detonation waves operate to alter the fluid flow.
According to another embodiment of the invention, a system for altering a fluid flow includes a lift fan shroud having a fluid flow generated by a lift fan, a detonation wave conduit adjacent the lift fan shroud, and a pulse detonation injection device coupled to the detonation wave conduit. The pulse detonation injection device is operable to inject a plurality of detonation waves in a pulsed manner through the detonation wave conduit to combine with the fluid flow to add thrust to the fluid flow.
Embodiments of the invention provide a number of technical advantages. Embodiments of the invention may include all, some, or none of these advantages. In one embodiment, fluid flow through a nozzle is controlled in a manner that allows throttling or vectoring of an engine""s thrust by providing pulsed injection of detonation waves. A fixed geometry nozzle may provide a combination of throttling and vectoring functions, depending on the positioning of ports in the wall of the nozzle. The use of pulse detonation injection devices can significantly reduce the weight, cost, and complexity of a jet engine and its associated nozzle. Pulse detonation devices reduce weight by eliminating or limiting the need for durable heavy moving parts, such as hinges, seals, actuators, hydraulics and other mechanical items necessary to open and close the typical iris type variable geometry nozzle. An aircraft equipped with an engine and fixed-geometry nozzle using pulsed detonation injection may also be implemented to non-circular exhaust aperture shapes typical of advanced fighter concepts. Efficiency of an engine is greatly improved since pulsed detonation injection provides pulsed cross flow with reduced or eliminated bleed air from the engine compressor, which can affect the mass flow rate of the primary fluid flow through the engine. An asymmetric cross flow can provide vectoring of an engine""s thrust. Thrust vectoring can allow aircraft control of pitch and yaw at all flying speeds, and can decrease the surface area of control surfaces, resulting in reduced aircraft drag and weight.
In another embodiment, fluid flow through a lift fan shroud is enhanced by providing additional thrust via pulsed injection of detonation waves. The use of pulse detonation injection devices can significantly reduce the weight, cost, and complexity of a lift fan system and its associated components while still providing additional adequate thrust.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.